Fire and smoke detector devices have been developed to alert occupants of rooms and buildings to take emergency action in the earliest stages of a fire. In many localities, ordinances have been enacted requiring the installation of smoke detector devices in all new and existing dwellings. Smoke alarm devices are available as battery powered units and as AC powered units. Permanently wired AC powered units are generally more expensive to purchase and usually require the services of an electrician. Battery powered smoke alarms are inexpensive and easy to install, although their effectiveness can be diminished by improper placement.
Battery powered units usually incorporate circuitry which causes a chirping signal or the like to be emitted when battery power drops below a threshhold level. Some units become unstable and emit false alarms when battery power drops to a level just above the threshhold. As a result, some residents consider smoke alarm devices to be a nuisance and fail to replace exhausted batteries, thus relinquishing the protection afforded by them. Battery powered smoke alarm devices, because of their low installation costs, are often provided in public housing units. A particular problem in such environments is that the units are often stolen.
In general, fire safety experts recommend that smoke alarm devices be placed near the ceiling of a room, and preferably near the center. In somewhat older homes, such a position is usually occupied by an existing light fixture. In newer homes without such ceiling fixtures, there are sometimes aesthetic objections to the placement of conventional smoke alarm devices in the center of a ceiling. In order to fulfill the needs of such circumstances, smoke alarm devices have been developed which incorporate light fixtures therein. Because of their use as light fixtures which will be switched on and off in the normal course of use, such devices are often powered by rechargeable batteries which are charged when the lamp is switched on. Smoke alarm devices with combined light fixtures are provided as hard wired, permanently mounted fixtures. These are suitable for a room with no ceiling fixture or as a replacement for an existing light fixture. However, they require professional installation.
Other types of smoke alarms with light fixtures include an integral threaded bulb base at one end for installation in an existing screw socket and a unit socket at the other end to receive a lamp bulb. A problem with the known devices of this type is that they retain the well known size and shape of conventional battery powered smoke detectors, that is, a flattened cylindrical shape of about six inches or greater in diameter. Devices of this shape are inappropriate for many existing fixtures since the alarm devices do not accommodate the diffusers or shades which form a part of the existing fixture. Thus, the resident is left with a bare bulb. Additionally, modern residential lighting often includes lamps mounted in so-called can light fixtures and track light fixtures. The dimensions of the broad cylindrical screw-in smoke alarms conventionally available will not fit within such fixtures. A problem with both permanently mounted and screw-in smoke alarms incorporating lamp sockets is that an electrical shock hazard exists in them when no lamp bulb is present in the unit socket.